Telegraph signal regenerator



Aug. 12, 1941.. KAHN' 2,252,380

TELEGRAPH SIGNAL REGENERATOR' Filed Feb. 2,9, mo 2 Sheets-Sheet 2[MARK/N6 PEAK 4a RECT/F/ED m2 em +8 l9 wscunnass 1 I149. 4b mvoasVOLTAGE 01 15 33 3/ J I 0 L33J B 32 8DISCHARGE$ 4L ANODE 11H VOLTAGE-0P5 v 0 v I LOCK/N6 cmcu/r ac. our ur FULL WAVE 'l-IALF WAVEREC'T/F/CATION RECTIFIER 24 Du: r0 RECT/F/ER4 90.6'H/F7' RESULT/INTRECTIFIER vozmas {ACROSS RESISTOR 27,

PEA/(5 OCCUR A THALF FREQUENCY RATE 1 INVENTOR. ALFR 0 KAHN ATTORNEY.

Patented Aug. 12, 1941 Alfred Kuhn, Hollis, N. Y., assignor to RadioCorporation of America, a corporation of Delaware Application February29, 1940, Serial No. 321,398

' 8 Claims. (cl. I'm-69.5)

This invention relates to a telegraph signal regenerator and moreparticularly to an electronic system for regenerating synchronoussignals which may havebeen deformed in traveling through the conductingmedium from the transmitter to the receiver.

It is an object of my invention to provide a regenerator which is simplein construction, easy to maintain, and which requires a minimum numberoi parts.

it is a more specific object of my invention to provide a regeneratorwhich eliminates, insofar as possible, mechanical commutation means, andwhich provides dependable regeneration of the received telegraphsignals.

It is a still further object of my invention to provide a regeneratorwhich depends for its oporation upon properly timed locally generatedimpulses, these impulses being coordinated with the received signals forcontrolling a so-called' .lociciug circuit oi conventional type.

In carrying out my invention I provide means dependent upon the normalrate of reception of the signalling elements for controlling amultivibrator. The output irequency of this multivibrator is held insynchronism by means well i-mown in the art. Such means may, forexample. be of the type shown and described in an application Serial No.169,365, tiled October 16,1937, by Richard E. Mathes, and assigned tothe assignee of the instant application. Mathes showed a synchronouscorrector applicable to a receiving distributor for a multiplex system.Such a corrector may be employed for maintaining the frequency and phaseof my multivibrator suitably coordinated withthe mean frequency ofreception of marking signal peaks. However, other means of control oithe multivibrator irequency may be adopted, whether mechanical orelectromechanical in structure, provided a source of substantiallyconstant frequency impulses is made available. This multivibrator isemployed in combination with rectified pulses representing markingelements of the telegraph signals so as to regenerate signals ofsubstantially squarewave formation, as is done when a. conventionalFigure 1 shows diagrammatically a preferred circuit arrangement forcarrying out the invention;

Fig.2 shows a typical wave shape representing the unfiltered output'iroma rectifier which in turn is controlled by a multivibrator;

Fig. 3 shows the wave shape oi output energy from an amplifier stagefollowing the rectifier whose output is as shown in Fig. 2;

Figs. to, db, 4c and 4d show respectively ditierent time graphs oisignals and voltages appearing across diilerent portions of the circuitarrangement:

Fig. 5 shows a detail oilmeans for utilizing a i multivibrator whosefrequency is equal to twice that of the signal frequency; and,

Figs. t and 7 show time graphs oi resultant impulses obtained by the useoi the means shown in Fig. 5.

Referring first to Fig. 1, I show a muitivibrator Mi? having an inputcircuit connected thereto which synchronizes its operation in dependenceupon a phase cox-rector unit PC, the latter being operative independence upon the arrival moments oi the signals. The output from themultivibrator is substantially sine wave in formatlen and is fed acrossa transformer l to the input circuit of an amplifier tube 2. The outputfrom this amplifier is fed across a transiormer t to a circuit whichincludes a full wave rectifier 4 and a load resistor 21. Thecathode orth r tifier. 4 is grounded and its anodes are connected to the terminalsof the secondary on the transformer II. This secondary has a midtapconnected to one terminal of resistor 21,

the other'terminal of which is connected to the grounded cathode.

An electron discharge tube 5 has a control grid connected to the mid-tapon the secondary of transformer 3. This tube is, therefore, controlledby the rectified voltage developed across resistor 21. The output fromthe tube 5 is utilized in a half wave rectifier tube 8 having in shunttherewith a resistor I of high ohmic value.

The unfiltered output from the rectifier 4 produces a wave shape asshown in Fig. 2. The tube locking circuit is properly controlled. Animportant'feature of my invention, therefore consists in the provisionof a circuit arrangement whereby the incoming signals and the oscillatorare caused to cooperate to control the locking circuit.

My invention will now be described in more detail, reference being madeto the accompanying drawings in which I is held at cut-oil by theaverage negative bias produced by the rectifier l and passes currentonly when the sharp bias peaks approach zero.

The anode voltage excursions or the tube I are shown in Fig. 3.

The purpose of the resistor I is to permit a slow charge to beaccumulated on the capacitor 8 during moments of peak voltage oithe'anode in tube 5. The tube 8, being conductive in one direction only,functions when tube 6 becomes conductive to permit the condenser 8 todischarge rapidly. I

The locking circuit is shown within a rectangular broken line encl andcomprises discharge tubes 26 and 2! in combination with a number ofresistive circuits interconnecting the electrodes and the power supplysource. The output leads from the locking circuit aredesignated L andmay be considered as feeding to a recorder unit or to keying means forretransmit acoasao signal. In case the spacing signal is prolongedbeyond the next instant of zero voltage drop across resistor Zl, theaction of condenser it will predominate over that of condenser 8, so

bias on the grid of tube iii to approach zero,

output from the tube ii is led across the primary of a transformer iswhose secondary has terminals connecting rvely with the anodes of a fullwave rectifier is. secondary isalso provided with a mid- -tap'connecting with one terminal of a load resistor iii and with the controlgrid in an amplifier tube is. The cathode of the rectifier it isconnected to a junction lead between resistors it and 27 so as toefiectively place the circuits of rectifier-s i and is in series.

A keyed tone signal is culled to transformers Iii and i2 and appears asa rectified signal voltage acrossresistor l6. condenser it so as tosmooth out the ripple com= ponent appearing in the rectified signal. Asuit able bias voltage is thereby obtained for controlling the grid oiamplifier tube iii.

The output from tube is is utilized in the some manner as the outputfrom tube b, but for the purpose oi operating the inciting circuit inthe reverse direction. "ihis is accomplished by means of a half waverectifier tube. to in aht with which is disposed a resistor ll of high cvalue. The anode of the rectifier it is connected to one side of thecondenser. is, the other side of which is connected tothc grid of tubeit in the locking circuit.

0n receptlonoi' the marking signal peaks, the rectified voltage acrossresistor it is a maximum and biases the tube to to cut oii. The voltageon the cathode of rectifier it floats between ground potential and thenegative potential derived from the rectifier .t, the latterheingprevalent most of the time and the former during the briefintervals of current interruption across resistor ll. During these brieiintervals the grid bias in tube l5 becomes slightly 1 negative than atother times. but not sufiicienily so for efiectinr; any control of tube2! in the locking unit;

On reception oi. a spacing signal simultaneously with the arrival of azero-voltage peek at the top end of resistor 2?, tube it drawssuiiicient current to enable condenser it to discharge substantiallyfully. This action results in blocs tube II at the negative wave crestoi a spacing T" resistor is shted W a that tube 2| will remain blockeduntil the arrival of succeeding marking signal. Thus, as shown in Fig.4b, the anode voltage of tube It dips slightly as at 80, and only onceat the crest of a short marmngsignal on (Fig. do), but dips repeatedlyas at 3| during a prolonged marking signal 1212. Here the periodic dips32 of anode voltage in tube 5 (Fig. 4c) are permitted to maintaincontrol'. Furthermore, during shortspace intervals 81 and long spaceintervals So the anode voltage oi tube l5 dips to its lowest value andblocking control of tube 2! is likewise maintained. The locking circuitwill, therefore, be tripped by the simultaneous occurrence of a spacingsignal peak and an impulse from the multivibrator MV. The action oi therectifier i6 and shunt resistor H is identical with that of rectifier 6and shunt resistor l, except that they follow the control of the spacingsignals, whereas the periodicity-of the latter is constant.

It will be seen from the above description that the tube it is eitherunblocked slightly by impulses from the rectifier it as when markingsignals occur, or is unblocked fully in the presence of spacing signalsplus an impulse from the rectifler i, in which case the rectifiedcurrent across the tube I8 is of suficient mplltude to fully dischargethe condenser is and thereby to bias the tube 2| to cut-ofl.This-simultaneous application ci' pulses from rectiflers 4 and it is inexcess of the discharge efiect across rectifier E alone and, therefore,the tube ill is controlled predominantly over the control of tube 25. Inother words, the sheet of the impulses from the multivibrator isswitched to control tube to for biasing the same to cut-ofi uponreception oil a marmng signal and is switched to control tube 25 uponreception of a spacing signal. The time oi occurrence of the pulses isheld to the center of each baud by means of the correction unit PC so asto pass the signal to the locking circuit during its best portion.

A typical time graph of a received signal representing dots and dashesand somewhat dismrted from the original square-wove form is Til shown into. Figs. 4b, 4c and 4d are time graphs drawn to the same time scale asPic. to. In Fig. 4b the anode voltage of tube iii is shown. The deepdepressions occur during spacinu intervals and represent times whentubes [8 and it are conductive. Tube it is only slightly urn-blocked atpeaks of the marking signal.

Fig. to shows voltage changes on the anode of tube 5 which result fromthe operation oi the multivibrator MN. The voltage is high for thegreater of the time because the rectifier i biases tube it substantiallyto cut-oil. Momentorlly, however, the output from rectifier t" issubstantially reduced to zero and the bias on the grid of tubeb rises tosubstantially zero, thus permitting the condenser 8 to discharge quicklyacross rectifier and the space path of the tube t. It is during thesedischarge intervals of condenser c that tube to in; the locking circuitis biased to cut-0d.

Fig. 4d shows the regenerated signal having a square wave formation.This is the signal which is delivered by the locking circuit at theoutput terminals 0L.

Referring now to Fig. 5, I show a detail of an arrangement wherein thecontrol frequency from the mammal minimise even though it possessestwicethe -frequencyfotthe signal ire!- rectifier 'l'is also the same as shownin Fig. i,

aasasso of a" train of received signals, means for continuouslycorrecting the phase or said generator quencyl Bu'ch'an arrangement hascertain pracwith respectto the marking wave peaks of said signals, afull-wave rectifier receptive of energy from said generator, a secondfull-wave rectifier receptive of tone frequency currents representingmarking signals, two series-connected load re- ,slstors, eachappropriately disposed in circuit but is supplemented by a half-waverectifier 24.

The phase of the voltage delivered to rectifier 24 is'in aquadraturerelationto the phase of the voltages delivered to the full waverectifier I. This is brought about by the use-oi a conventional systemof capacitor}? and resistor R in series with oneanother, theinterconnection between them being also connected to the anode of therectifier 24. The cathodes of the rectifiers l and rare interconnectedand lead to thegrounded end oi! resistor 21. The other end of resistor21 is connected with the mid-tap on the secondaryfo! transformer i, thesame as shown inFig.l. 4

By means of the arrangement shown in Fig. 5 certain voltages aredelivered across. resistor 21 as shown in Fig. 8. The combinedrectifiervoltage, however, is shown in Fig. 7. It will be noted that thesharp peaks of no voltage appear only at every other cycle of themultivibrator frequency, intervening voltage dips being counteracted bythe output from the half-wave rectiher 24. It is only the negative peakswhich represent substantially no voltage across resistor of that typehas been disclosed by a. a. Shenk in his application Serial No. 326,902,filed March 30, 1940. It will also be understood by those skilled in theart that various modifications or the invention may be adopted withoutdeparting from the soiritfand scope of the invention as defined by theclaims to follow.

I claim:

1. In atelegraph signal reseneramr, a lock ing circuit for keyingflthemarking impulses of a signal train. a multivibrator capable of eneratingself-sustained oscillations subject to phase correction by a train ofreceived signals. means responsive to the operation of saidmultivibrator for timing the shifts of said locking circuit from one toanother state of electrical stability, means operative during receptionof. the wave peak. of a marking signal of baud unit length for producingone of saidshiits in one sense, means operative during the reception ata wave valley representing a spacing B InaI oi' baud unit length forproducing one of said shifts in the opposite sense, and means inherentin the cooperative" with a respective one of said rectifiers. and meanscomprising two capacitive circuits forproducing shifts in oppositesenses of electrical stability of said locking circuit, each 'of saidcapacitive circuits including means for slowly storing a charge when anassociated one of said lead resistors draws current, and forsuddenlydissipat- 'ing said charge when that resistor ceases to drawcurrent. I

3. The combination, according to claim 2, in which the stated means ineach of said capacitive circuits is constituted by a half wave rectifiershunted by a resistor. I

- 4. The method of controlling a locking circuit for the purpose ofregenerating telegraph signals received at a substantially fixed baudfrequency, which comprises generating a sine wave, continuouslycorrecting thephase of said wave in accordance with said receivedsignals, separately rectifying the energies of said wave and of themarking elements of said signals, slowly accumulating' a capacitivecharge during each moment Of rectification or the sine wave energy,slowly accumulating another capacitive charge during reception of eachmarking signal element, periodically and .suddenly dissipatingthe firstmentioned charge at said-baud frequency, suddenly dissipating the secondmentioned charge simultaneously with the first whenever thereception ofa spacing signal is coincident, causing said locking circuit to shiftfrom a first to a second state of electrical stability in response tothe dissipation of the first mentioned charge only,

and causing said locking circuit to shift in an opposite sense inresponse to the simultaneous dissipation of both said charges.

5. A telegraph signal regenerator comprising a locking circuit havingtwo discharge tubes,

the-electrodes of which are resistively interconnected in such mannerthat one isnormally blocked while the other draws current and the actionof the aforesaid means for continuing the state of electrical stabilityto which said locking circuit is shifted during the prolongation of.markingandspacingsignalsbeyondanintervalof band unit length.

2. In a-telegraph signal regencrator, a locking circuit for keying themarking impulses of a signal train, an oscillation generator having asubstantialiy-sine-wave output at a irequency' blocking of each tube byan extraneous negative impulse causes the other tube to becomeconductive, each tube having a blocking bias circuit connected betweenits cathode and control grid, each said control grid being coupledthrough an appropriate storage capacitor to a suitable COD! trolcircuit, a source of periodic impulses delivered at a baud-frequencyrate corresponding to the speed of reception of a train of telegraphsignals, a full-wave rectifier responsive to said impulses, a secondfull-wave rectifier responsive to received tone frequency energyrepresenting marking elements of said signals, two inverter tubes, eachunder the respective control of one of said rectifiers, and means ineach of said control circuits for eii'ecting a slow charge and a rapiddischarge of its appropriate storage 'capacitor in response totheblocking and unblocking respectively 01' an appropriate once! saidslsnal'and to cause the second capacitor to dis.-

charge more effectively than the first during reception-of aspacingsignal.

time; approximating the baud unit periodicity is c. In a telegraphsignal regenerator a locking circuit rtr re-shaping the marking impulsesor aslgnaltraimsaidmarkingimpulsesbeingof normal length equal to a buud'and multiples thereof, and being separated by spacing intervals lockingcircuit from one to another state of electrical stability, meansresponsive tothe reception of signals to be re-shaped for correcting thephase of said oscillator, means under control of aesaseo hair to bere-shaped for correcting the phase of said oscillator, means undercontrol of said oscillator for producing short sharp impulses ofbaudfrequency, and means under the joint control ofthereceivedsignalsandofthelastsaidmeans for fixing the moments when theelectrical staself-sustained oscillations subjectto p a corsaidoscillator for producing short sharp impulses of baud-frequency; andmeans under the Joint control of the received'signals and of the lastsaid means for fixing the moments when theelectrical stability of saidlocking circuit is ing a normal frequency equal to the baud frequencyfor timing the shifts of said locking circuit from one to anotherstate'of electrical stability, means responsive to the reception-ofslarection by a train of received signals, means re sponsive to theoperation-of said oscillator for, timing the shifts of said lockingcircuit from one to another state of electrical stability, meansoperative during reception of the wave peak of a marking signal of baudunit length for producing one of said shifts in one sense, meansoperative during the reception of a wave valley representing a spacingsignal of baud unit length for producing one of said shifts in theopposite sense, and means inherent in the cooperative action of theaforesaid means for continuing the state of electrical stability towhich said locking circuit is shifted during the prolongation of markingand spacing signals beyond an interval of baud unit length.

